1. Technical Field
This invention relates to an imaging system and method which captures arrival time and position information associated with each photon of an incoming photon stream, for use in image construction.
2. Background Information
In conventional photography, an image is recorded by opening the shutter for a predetermined length of time, and accumulating all the light that passes through an aperture onto a photosensitive surface such as conventional photographic film. More recent approaches use arrays of CCD pixels as the photosensitive surface, to generate digital images. Although the use of surfaces such as CCD arrays may represent improvements relative to chemical-based photographic film, both approaches are subject to many of the same drawbacks. For example, both processes are subject to issues such as overexposure, underexposure, and blurring due to excessive camera movement relative to shutter speed. Once the image is recorded using these conventional approaches, there is little that may be done to adjust for these issues, particularly with respect to blurring.
U.S. Pat. No. 5,912,993 (the '993 patent) and U.S. Pat. No. 6,018,365 (the '365 patent) both of which are fully incorporated herein by reference, disclose techniques for generating an image based on individually read CCD pixels. These approaches use image position information inferred from CCD pixel position to generate the final image. The image reconstruction technique of the '993 patent works by looking for an underlying configuration of “pixons” that best fits the original, noisy and distorted, image, but with the noise and distortion removed. This method operates on an already captured image.
In the '365 patent, the CCD is read out many times, clearing out the charge building up in the pixels, over an interval that would otherwise over-expose the CCD. In doing so, the process keeps the over-exposed pixels from “blooming” out and bleeding into the image in the surrounding pixels. This is thought to facilitate an increase in the contrast range of the CCD, e.g., to permit the photographing of scenes with large differences between areas of light and dark (e.g. as occurs at sunset, or headlights at dusk). Once these sub-images are collected, an image may be constructed.
While these patents may address some of the aforementioned drawbacks, there remain a number of unresolved issues, such as those associated with blurring due to camera movement.